1. Field of the Invention
This invention relates to laminated glass structures. This invention particularly relates to laminated glass structures that can withstand severe impact and/or severe pressure loads.
2. Description of the Prior Art
Conventional glazing structures comprise a glazing element. Such glazing elements can comprise a laminate window, such as a glass/interlayer/glass laminate window. There are various glazing methods known and which are conventional for constructing windows, doors, or other glazing elements for commercial and/or residential buildings. Such glazing methods are, for example: exterior pressure plate glazing; flush glazing; marine glazing; removable stop glazing; and, silicone structural glazing (also known as stopless glazing).
Threat-resistant windows and glass structures are known and can be constructed utilizing conventional glazing methods. U.S. Pat. No. 5,960,606 ('606) and U.S. Pat. No. 4,799,346 ('346) each describes laminate windows that are made to withstand severe forces. In International Publication Number WO 98/28515 (IPN '515) a glass laminate is positioned in a rigid channel in which a resilient material adjacent to the glass permits flexing movement between the resilient material and the rigid channel. Other means of holding glazing panels exist such as adhesive tapes, gaskets, putty, and the like can be used to secure panels to a frame. For example, WO 93/002269 describes the use of a stiffening member, which is laminated to a polymeric interlayer around the periphery of a glass laminate to stiffen the interlayer, which can extend beyond the edge of the glass/interlayer laminate. In another embodiment, '269 describes the use of a rigid member, which is inserted into a channel below the surface of a monolithic transparency, and extending from the transparency.
Windows and glass structures capable of withstanding hurricane-force winds and high force impacts are not trouble-free, however. Conventional glazing methods can require that the glazing element have some extra space in the frame to facilitate insertion or removal of the glazing element. While the additional space facilitates installation, it allows the glazing element to move in a swinging, rocking, or rotational motion within the frame. Further, it can move from side to side (transverse direction) in the frame depending upon the magnitude and direction of the force applied against the glazing element. Under conditions of severe repetitive impact and/or continuous pressure, a glass laminate can move within the frame or structural support in such a way that there can be sufficient stress built up to eventually fracture the window and allow the laminate to be pulled out of the frame. For example, when subjected to severe hurricane force winds the flexing movement in the windows of IPN '515, wherein glass flexes within a rigid channel, can gradually pull the laminate out of the channel resulting in loss of integrity of the structure. In '346, the glass held against the frame can be broken and crushed, causing a loss of structural integrity in the window/frame structure. In WO '269, inserting a stiff foreign body into as described therein can set up the structure for failure at the interface where the polymer contacts the foreign body when subjected to severe stresses.